Passive stabilization system



April 2, 1963 K. c. RIPLEY 3,083,673

PASSIVE STABILIZATION SYSTEM Filed Oct. 25, 1960 FIG. I.

FIG. 2.

INV EN TOR Kenneth Clay Ripley ifma wgm ATTORNEYS United States i ate 3,083,673 PASSIVE STABILIZATION SYSTEM Kenneth Clay Ripley, Washington, D.C., assignor to John J. hicl'vlnilen Associates, Inc., New York, N.Y., a corporation of New York Filed Oct. 25, 1960, Ser. No. 64,934 2 Claims. (Cl. 114-125) The present invention relates to a novel passive stabilization system for vessels.

It is already known that vessel stabilization against rolling can be achieved through the use of passive stabilization systems incorporating velocity squared damping. This is basically achieved by establishing spaced liquid storage points athwartship and interconnecting them by means of a liquid duct characterized by velocity squared damping means located at the junction of the duct with the liquid storage points. In a specific design, a pair of tanks are located on opposite sides of a vessel and are interconnected by means of a liquid crossover duct which also serves as an air interchange for the two side tanks. In this way, the air pressure above the liquid is equalized at all times at all points in the system. Nozzle designs are located at the junction points between the side tanks and the crossover duct. In a particular embodiment, the nozzle designs are simply vertical pipes located in spaced, transverse relation with reference to the side tanks and crossover duct. This system has been demonstrated to provide exceptional stabilization against rolling.

It has become evident, however, that the system as described is tunable only to a narrow band response about the resonance of the vessel. The present invention seeks to cure this deficiency by providing an improved passive stabilization system of the type described above characterized by a broadened response. This is essentially accomplished by providing a plurality of stabilizing units, each arranged with different tuned characteristics. This is achieved by providing the side tanks of the plurality of stabilizing units with different free surface areas. It is appreciated that tuning of a stabilizing system of the type described can be achieved by adjusting the liquid level in the system. Thus, an alternative technique or structure for accomplishing the broadened response described would be to provide a plurality of units characterized by the same free surface areas for the side tanks thereof and to use different liquid levels in each unit. However, the objection to this method is that in adjusting the tuning the damping characteristics of the system are changed. This solution to the tuning problem can only be carried so far without modifying the damping to an extent which might be objectionable. For this reason, these two alternatives cannot be considered equivalent.

Accordingly, it is a principal object of the present invention :to provide a passive stabilization system of the type described characterized by a broadened response.

It is a further object of the present invention to provide a novel passive stabilization system for a vessel which functions more etficiently and expediently under a greater variety of conditions than systems heretofore known.

Other and further objects of the present invention will become readily apparent from the following detailed description of a single preferred embodiment of the present invention when taken in conjunction with the appended drawings in which:

FIGURE 1 is a view in section of the novel stabilization system of the present invention taken along line 1-1 of FIGURE 2; and

FIGURE 2 is a view in section taken along line 2-2 7 of FIGURE 1.

3,083,673 Patented Apr. 2, 1963 Referring now to the drawings in detail, a specific preferred embodiment of the present invention will now be described. The stabilization system is shown comprised of a top wall 20, a bottom wall 22, side walls 24 and end walls 26 which together define a completely enclosed compartment of rectangular parallelepiped configuration. The inside of the compartment is sub-divided into three elongated compartments by means of bulkheads 28 which extend parallel to side walls 24 between end walls 26. Pairs of vertical pipes 30, 32, 34, 36, 38, 40, 42, 44, and 46 are mounted in spaced transverse relationship at intervals in the three compartments. Each pair of pipes defines a nozzle to act upon the liquid contained in the compartments to the level indicated by reference numeral 48 to produce velocity squared damping. Liquid-usually oil or wateris placed in each of the three compartments to the 'level 48, which level is determined as a result of prior calculation taking into account the assigned frequency of the unit. For instance, the three compartments can be tuned to the frequency of the vessel, 1.075 times the frequency of the vessel, and 1.15 times the frequency of the vessel, respectively. These figures are given merely by way of illustration and should not be construed as placing any limitation upon the invention.

Flat bars 50 are fixed to the center line of walls 24 and 26 and bulkheads 28 and act as swash means to inhibit wave action and also serve as a reinforcement.

The reason for having some of the units detuned from the frequency of the ship is that this takes into account the combined roll and sway of the ship in the seaway and enables one to get the net result desired which is a pure damping moment at ships resonance. The nozzle structures defined by pipes 30, 34, 36, 40, 42, and 46 at either end of the compartments serve to divide the compartments into three main sections. The end sections, those outward of the designated nozzle designs, constitute liquid storage tanks. The spaces between the designated nozzle arrangements constitute liquid crossover sections. The principal energy dissipation or damping occurs as the liquid is transferred into and out of the liquid crossover sections due to the rolling motion of the vessel. The nozzle structures defined in the center of the compartments by the pipes 32, 38, and 44 serve as a means to dampen wave action in the liquid crossover duct sections. These nozzle structures are designed so that they will not be a primary source of the damping, but a secondary source of the damping. The center nozzle structures (pipes 32, 38, and 44) supply from about onetenth to about one-(fifth of the total required damping in order not to detract too much from the damping provided by the main nozzle structures (pipes 30, 34-, 36, 40, 42, and 46).

The stabilizing arrangement of the present invention has been shown as comprised of three stabilizing units. It will be appreciated that any number of stabilizing units can be banded together in this fashion. Also, the stabilizing units have been shown as placed together in a longitudinal ararngement, that is parallel with one another. It is equally possible to arrange them transversely so that their longitudinal axes are coincident or parallel.

The stabilizing arrangement, as described, is located athwart the vessel to be stabilized between a pair of decks 52 and 54. The actual location of the stabilizing arrangement as regards elevation, etc., is a matter of design and choice. Essentially, the higher in the vessel the location of the stabilizer, the smaller it can be made. It will also be appreciated that the stabilizer may comprise a series of stacked units as well as units arranged side by side or end to end or, alternatively, the units may be independently located altogether.

Although: the invention has been shown and. described in terms of a specific preferred embodiment, it will be appreciated that various changes and modifications will occur to those skilled in the art from a knowledge of the teachings oftthe present invention. Such changes-as are obvious are deemed to come within the purview of the invention.

What is claimed is: 1. The combination of a vessel and a stabilization system therefor comprising a plurality of units each composed of an elongated enclosure extending transversely across said vessel, Wall means compartmenting said enclosure todefine a wing tank on each end of said enclosure and an interconnectingcentral com artment, said wall means defining restricted vertically elongated openings communicating said wing tanks and said central compartment with the openings beingshaped to cause substantial jet loss of head firom liquid passing therethr'ough, and a body of liquid in said enclosure having a; liquid level such that in a repose horizontal condition the o enings defined in said Wallrneans extend substantially above and below the level of the liquid to provide unrestricted passage for air and restricted passage for liquid, the cross interconnecting said win-g tanks, said duct and said wing tanks mutually defining restricted communicating vertically" elongated openings to produce asubstantial jet loss of head from liquid passing therethrough, liquid in said wing tanks and said duct at a uniform level throughout said system which level is spaced substantially below the top of said wing tanks and said duct when the system is in a repose horizontal condition, and said wing tanks and said duct defining a continuous airspace, including the upper portion of said restricted communicating openings, above the level' of liquid which allows for the free unrestricted exchange and equalization of air as between said wing tanks and said duct, the cross sectional areas of said wing ta'n'ks being different for said plurality of units whereby said units are tuned to different frequencies.

References Cited in the file of-thispatent UNITED STATES" PATENTS 1,023,477 Oldham Apr. 16, 1912 2,077,143 v Carroll Apr. 13,. 1937 FOREIGN PATENTS" 13,784 Great: Britain of i908 435,100 Great Britain Sept .15, 1935 675,003 Germany Apr. 27, I939 911,182 France Mar. 4, 1946 OTHER REFERENCES- Ser. No. l32,6-95, Hort (A.P.C.)', published May ll, I943. 

1. THE COMBINATION OF A VESSEL AND A STABILIZATION SYSTEM THEREFOR COMPRISING A PLURALITY OF UNITS EACH COMPOSED OF AN ELONGATED ENCLOSURE EXTENDING TRANSVERSELY ACROSS SAID VESSEL, WALL MEANS COMPARTMENTING SAID ENCLOSURE TO DEFINE A WING TANK ON EACH END OF SAID ENCLOSURE AND AN INTERCONNECTING CENTRAL COMPARTMENT, SAID WALL MEANS DEFINING RESTRICTED VERTICALLY ELONGATED OPENINGS COMMUNICATING SAID WING TANKS AND SAID CENTRAL COMPARTMENT WITH THE OPENINGS BEING SHAPED TO CAUSE SUBSTANTIAL JET LOSS OF HEAD FROM LIQUID PASSING THERETHROUGH, AND A BODY OF LIQUID IN SAID ENCLOSURE HAVING A LIQUID LEVEL SUCH THAT IN A REPOSE HORIZONTAL CONDITION THE OPENINGS DEFINED IN SAID WALL MEANS EXTEND SUBSTANTIALLY ABOVE AND BELOW THE LEVEL OF THE LIQUID TO PROVIDE UNRESTRICTED PASSAGE FOR AIR AND RESTRICTED PASSAGE FOR LIQUID, THE CROSS SECTIONAL AREAS OF SAID WING TANKS BEING DIFFERENT FOR SAID PLURALITY OF UNITS WHEREBY SAID UNITS ARE TURNED TO DIFFERENT FREQUENCIES. 